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Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.10.0 Subject: Re: [PATCH v3 1/2] drivers: usb/core/urb: Add URB_FREE_COHERENT Content-Language: en-US To: David Laight , 'Greg Kroah-Hartman' Cc: 'Vincent MAILHOL' , Alan Stern , Marc Kleine-Budde , Rhett Aultman , "linux-usb@vger.kernel.org" , linux-can , Oliver Neukum References: <20220610213335.3077375-1-rhett.aultman@samsara.com> <20220610213335.3077375-2-rhett.aultman@samsara.com> <20220611153104.sksoxn4dmo5rgnk3@pengutronix.de> <48caa879b0064ced97623bf1dad5b2d9@AcuMS.aculab.com> <186561fa929f459985ad2986936988e5@AcuMS.aculab.com> From: Oliver Neukum In-Reply-To: <186561fa929f459985ad2986936988e5@AcuMS.aculab.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-ClientProxiedBy: AS9PR06CA0545.eurprd06.prod.outlook.com (2603:10a6:20b:485::15) To VI1PR0401MB2526.eurprd04.prod.outlook.com (2603:10a6:800:58::16) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: 5cb4d597-26cc-4873-deb9-08da543fefbf X-MS-TrafficTypeDiagnostic: AM0PR04MB6788:EE_ X-LD-Processed: f7a17af6-1c5c-4a36-aa8b-f5be247aa4ba,ExtFwd X-Microsoft-Antispam-PRVS: X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; 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That is just as hard to do for DMA coherency. > Indeed for XHCI there is a bit that allows 8 bytes of data to > replace the pointer in the ring structure itself. > I don't remember the driver every doing that. XHCI does use it. There was even a bug with endianness. Regards Oliver